Visco-elastic or rubberlike materials occupy a special place in today's .engineering because of the unique property of resilience. Every year scientists are reporting about new rubberlike polymers with exciting properties and potential applications for automobile, marine and aerospace industries. Despite the fact that the dynamics of rubberlike materials has been investigated intensively since early 1940s, the number of non-destructive testing methods is still limited mainly because rubberlike materials are acoustically weak, i.e., conventional ultrasonic testing is hardly applicable. Todays users are left to rely on the specification provided by a maker or manufacturer of the material.
Available non-destructive test methods are classical hardness testing and x-ray examination. Such test methods typically require large size test instruments or test instruments which are not portable and must be used in a laboratory environment. Crucial disasters due to the failure of rubberlike materials, some which have involved many casualties, illustrate a need for the highly reliable non-destructive test methods and devices. Such disasters include the explosion of the space shuttle Challenger in 1986, caused by failure of "O" rubber rings at the liquid oxygen tank and the sinking of the Estonian ferry boat in the Baltic Sea in 1995, caused by non-functioning of rubber isolation seals at the front door. It is obvious that new standards and methods for non-destructive testing of rubberlike parts in-situ should be developed in order to reliably test these materials.